About 1 in 7000 patients awakening from anesthesia experience dental injuries known as “Emergence Clenching Dental Trauma.” This is reportedly the most common cause of malpractice claims against anesthesia providers.
According to the American Society of Anesthesiologists, the problem is that “Placement of an airway device (oropharyngeal airway, Laryngeal Mask Airway, Endotracheal Tube) transfers jaw clenching forces forward to two or more incisors.” This is problematic because, although healthy molars and premolars tolerate vertical forces of 100-200 lb. in most patients, anterior teeth tolerate vertical forces of only 25-35 lb. and horizontal forces of less than 25 lb. Diseased or restored teeth are particularly vulnerable to injury.
The conventional solution is to “transfer clenching pressures backward and distribute the forces among the more tolerant molar teeth” using a combination airway/bite block. Commonly used airway/bite blocks include the Guedel oropharyngeal airway, the Cobe oropharyngeal airway, Williams airway intubator, Patil oral airway, Ovassapian fiberoptic intubating airway, modified Connell airway, Mehta's cuffed oropharyngeal airway, other cuffed oropharyngeal airways, the bite blocks for use in dentistry and for use in conjunction with laryngeal mask airways and endotracheal tubes. Additional examples of attempts to address the issues described above include those patents listed below. These and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
Patent No.Issued DateInventor4,270,529June 1981Muto4,351,331September 1982Gereg4,425,911January 1984Luomanen4,495,945January 1985LiegnerD283,158March 1986Jackson4,640,273February 1987Greene et al.5,009,227April 1991NieuwstadD329,901September 1992Jackson5,174,284December 1992Jackson5,305,742April 1994Styers et at.D348,932July 1994Jackson5,413,095May 1995WeaverD399,950October 1998Shepard6,257,238July 2001Meah
Conventional oropharyngeal airways and combination airway/bite blocks generally suffer from significant defects. Perhaps the most significant problem is that they test to be symmetric about the midline, where the teeth are far more susceptible to damage from “emergence clenching.” Other problems include: interference with tongue retraction necessary to maintain an open airway; interference with bag-mask ventilation, which may be a necessary rescue effort on induction and/or emergence from anesthesia and sedation; excessive jaw opening beyond the comfort range of many patients; a presence of acute angles that increase the risk of soft tissue damage; and lack of disposability.
What are still needed are systems, methods and devices that satisfactorily maintain an open airway while preventing emergence clenching.